1. Technical Field
The present invention relates to print-based surface-encoding schemes; more particularly the invention relates to novel clustering-definition-based encoding schemes printed onto a physical surface whereby the surface can function as an interface providing orientation feedback.
2. Description of the Related Art
The technology for making the information coded as bit data and an electronic document correlate and unify within a printed document is known well.
The concept of 1-dimensional or 2-dimensional barcodes and the usage for acquiring the positional information on a document based on the information added to the printed document is disclosed (refer to Patent References 1-8, for example).
An invention which unifies barcodes of different dimensions is also disclosed (for example, Patent Reference 9). As a specific example, a digital information carrier wherein 1-dimensional and 2-dimensional layers are unified is shown there.
A barcode of 1-dimensional and 2-dimensional layers having a multilayer structure is also disclosed (for example, Patent References 10 and 11).
It is also disclosed how to integrate a barcode in an image or a secret document (for example, Patent References 12-19).
A data coding method performed using an illustration symbol is also disclosed (for example, Patent References 20 and 21).
A method for coding by using at least two sorts of symbols and arranging these symbols in a matrix shape on various media wherein a document display is possible (for example, Patent Reference 22) is also disclosed. As a specific example it is shown how to use a monochrome lattice-like pattern.
The method of combining a plurality of 2-dimensional dot codes using different colors is also disclosed (for example, Patent References 23-26).
Dot Code
A technology based on a self-synchronous type of symbols called “glyphs” is also disclosed (for example, Non-Patent Literature 1). It is indicated that glyph positions provide for the glyph clocking mechanism, and that glyph orientations provide for information to be digitally encoded.
In addition, a method for showing positional information using glyphs over the whole predetermined region of a document is also disclosed (for example, Patent Reference 27). It is indicated that each glyph is shown by a line segment inclined to the left or to the right that provides for 1 bit of information. Furthermore, other glyphs which can code 2 bits of data are disclosed (for example, Patent Reference 28). It is indicated that such glyphs are expressed in a triangular shape and have four different directions, this providing for 2 bits of information per glyph.
In any of the prior art, however, the problem of recognition errors is not completely overcome. Reasons for recognition errors can be classified into several cases which will be explain here.    Patent Reference 1: U.S. Pat. App. Pub. No. 2002/0027165    Patent Reference 2: U.S. Pat. No. 6,418,244    Patent Reference 3: U.S. Pat. No. 6,176,427    Patent Reference 4: U.S. Pat. No. 5,617,358    Patent Reference 5: U.S. Pat. No. 6,070,805    Patent Reference 6: U.S. Pat. No. 5,742,041    Patent Reference 7: U.S. Pat. No. 6,043,899    Patent Reference 8: Japanese Unexamined Pat. App. Pub. No. H07-306904    Patent Reference 9: U.S. Pat. No. 6,398,117    Patent Reference 10: Japanese Nat'l. Stage Pub. of Int'l. App. WO96/18972    Patent Reference 11: U.S. Pat. No. 5,525,798    Patent Reference 12: U.S. Pat. No. 5,525,798    Patent Reference 13: U.S. Pat. No. 6,256,398    Patent Reference 14: U.S. Pat. No. 5,522,623    Patent Reference 15: U.S. Pat. App. Pub. No. 2002/0060396    Patent Reference 16: European Pat. No. 1 154 373    Patent Reference 17: Japanese Unexamined Pat. App. Pub. No. 2001-320573    Patent Reference 18: Japanese Unexamined Pat. App. Pub. No. 2002-36763    Patent Reference 19: Japanese Unexamined Pat. App. Pub. No. 2002-63142    Patent Reference 20: French Pat. No. 2,809,210    Patent Reference 21: U.S. Pat. No. 6,460,766    Patent Reference 22: U.S. Pat. No. 6,273,340    Patent Reference 23: European Pat. No. 1 178 428    Patent Reference 24: Japanese Unexamined Pat. App. Pub. No. 2000-293644    Patent Reference 25: Japanese Unexamined Pat. App. Pub. No. 2000-293645    Patent Reference 26: Japanese Unexamined Pat. App. Pub. No. 2000-293646    Patent Reference 27: U.S. Pat. No. 6,327,395    Patent Reference 28: U.S. Pat. No. 5,245,165    Non-Pat. Document 1: Hecht D., “Printed Embedded Data Graphical U.S.er Interfaces,” Computer, March 2001, pp. 47-55Ghost Dots
It means appearance of noise and stains, such as blots that occur at the time of printing. When a digital information carrier is constituted by dots, this has significant impact and it is commonly addressed by defining a lattice for arranging and removing image objects.
Recognition Errors Due to Display Distortion
This occurs when an image object is displayed or recognized while deviating from the ideal form at the time of displaying or reading a digital information carrier. Specifically, at the time of displaying the cause is variation in the sending and printing speed, and at the time of reading the cause is variation in the scanning speed of a scanner, tilt of a camera, etc. This influence becomes significant, especially with multiple image objects, such as two dimensional codes. In addition to display distortion, when coding bit data in the color of an image object, the gap from the ideal color, that is, the color difference, similarly leads to recognition errors.
Recognition Errors Due to Incorrect Recognition of the Coordinate System
Incorrect information will be generated, for example, if a digital information carrier is read while the document is upside down and it is decoded without taking that into account. This becomes especially problematic when highly symmetrical image objects are used.
Other Recognition Errors
When there is an image object that is partially difficult to recognize in the recognition range, the whole image object in the recognition range may become impossible to decode, or may be incorrectly recognized. This becomes especially problematic when acquiring one piece of information from a group consisting of a plurality of image objects in a predetermined range.
When attempting to increase the amount of retained information of a digital information carrier, the display density of the image becomes high, and the possibility of the above-mentioned incorrect recognition increases. In addition, it is also problematic when measures performed in order to avoid incorrect recognition reduce the display flexibility of a digital information carrier, or complicate the processing for acquiring information and reduce the processing speed.
Therefore, a digital information carrier which can easily display large volume of information, has low possibility of incorrect recognition, and is easy to process at high speed is called for.